1. Field of the Invention
The present disclosure relates to power substations generally, and more particularly, to a new pushbutton incorporated into new circuit configurations of an improved intelligent electronic device (“IED”) for use in power substation control systems.
2. Discussion of Related Art
Power substations include primary equipment, such as transformers, capacitor banks, and generators; and secondary equipment, such as cables, switches, relays, protective equipment, and control equipment. Primary equipment is located in the substation yard and controlled via (fiber-optic and/or metallic) cables. Providing all weather protection and security for the control equipment, a substation control house contains switchboard panels, batteries, battery chargers, supervisory control equipment, power-line carriers, meters, and relays. Located within the control house, the switchboard control panels contain meters, control switches, and recorders used to control the substation equipment, to send power from one circuit to another, or to open or close circuits when needed.
In the past, hundreds of discrete electromechanical and/or solid-state control devices were needed to monitor and manage the operation of a single substation's primary equipment. Recently, microprocessor-based devices, called intelligent electronic devices (“IEDs”), have become popular, not only because a single IED can be programmed and configured to monitor and manage a variety of substation equipment, but also because new substations constructed using IEDs cost less to construct than substations constructed using electromechanical and/or solid-state control devices. Properly positioned and configured, an IED can receive and relay status signals from primary equipment to a master computer located in the control house. Additionally, an IED can receive and relay command signals from the master computer to the primary equipment. The large majority of substation functions have been merged into the IED. However, local control of substation equipment remains problematic. This is due to the fact that the IED is necessarily more complex and therefore has a lower reliability that the simple mechanical pushbutton it replaces.
Problems arise when an IED fails, since transmission of status signals from its associated primary equipment and transmission of control signals from the master computer to the associated primary equipment stop. Manufactured to interrupt heavy power loads, mechanical pushbuttons tend to be heavy and bulky. A mechanical pushbutton is known to have been directly and externally connected to the input/output terminals of an IED. Such a configuration is problematic on several levels. Not only is the mechanical pushbutton a significant proportion of the size of the IED itself, but also the mechanical pushbutton is capable of interrupting thirty or more amps of current. Such a pushbutton is too large and cumbersome to be easily incorporated into an IED.
What is needed is a new, non-mechanical, pushbutton that easily integrates within an IED, handles only a small amount of current (e.g., less than one amp), and is configured to control substation equipment if the IED fails.